1. Field of the Invention
The present invention relates to an apparatus and a method for analyzing an electric field or discharge in a transfer process.
2. Description of the Related Art
Japanese Patent Laid-Open No. 2004-138891, discloses a method for analyzing an electric field or discharge in a charge process and a transfer process in an electrophotographic apparatus. In this method, a Poisson equation is solved, considering charge transfer in a conductor according to Ohm's law and gaseous discharge between a dielectric and a conductor according to Paschen's law, to calculate an electric field in a transfer process.
FIG. 3 shows a two-dimensional model of a transfer process to be analyzed for an electric field. The model shown in FIG. 3 shows a transfer roller 30, a core metal 31 of the transfer roller 30, a voltage 32, a counter roller 33, a transfer belt 34, a paper sheet 35, and a support roller 37.
In FIG. 3, the transfer roller 30 opposes the grounded counter roller 33. The transfer belt 34 and the paper sheet 35 are sandwiched between the transfer roller 30 and the counter roller 33 and pressed against each other. The pull angle of the upstream portion of the transfer belt 34 is adjusted by the support roller 37, and the downstream portion of the transfer belt 34 is wound around the counter roller 33.
In an actual apparatus, the positive voltage 32 is applied to the core metal 31 of the transfer roller 30 to transfer toner put on a surface of the transfer belt 34 on the side of the paper sheet 35. In this case, the transfer roller 30, the counter roller 33, the transfer belt 34, and the paper sheet 35 are rotated or moved from the right to the left in the direction of an arrow. The entrance side of a nip (the right of the nip) is called the upstream portion, and the exit portion of the nip (the left of the nip) is called the downstream portion.
FIG. 4 is an enlarged diagram showing a part that is surrounded by a broken line and includes the nip and the neighborhood in FIG. 3. A model in FIG. 4 includes air areas 36, resistive layers 38, and a minute gap 39. In electric field calculation, the resistive layers 38, which are nipped contact portions, need to be set up. Moreover, when electric field analysis in which toner is considered is performed, the minute gap 39 corresponding to the thickness of a toner layer needs to be set up between the transfer belt 34 and the paper sheet 35.
Parameters necessary for two-dimensional electric field analysis for such a transfer process apparatus include, for example, the conductivity and permittivity of each of the transfer roller 30, the transfer belt 34, the paper sheet 35, and the like, the amount of toner charge, and data on the shape of a nip at which these members are pressed against each other.
However, the following problem exists in the forgoing known analysis technique.
The same mesh model cannot be used in electric field calculation and structural calculation. This is because, in electric field calculation, resistive layers that are contact portions and a minute gap for a toner passage are necessary, but in structural calculation, these elements are not considered. This is also because respective analysis regions and necessary analysis accuracies in electric field calculation and structural calculation differ from each other. Moreover, when, in view of operations in a transfer process, in structural analysis, the movement of the leading end of a soft medium (paper), the movement changing every moment, is considered as the movement of a mesh, in electric field calculation, a mesh needs to be redivided for each time step. In electric field calculation in which resistive layers that are contact portions and a minute gap are considered, the process of redividing a mesh requires a great deal of calculation time.
These problems affect quantitative evaluation of image degradation, thereby significantly affecting the practical use of simulations.